flask-SQLAlchemy的ORM
1.创建表
import datetime from sqlalchemy import create_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index from sqlalchemy.orm import relationship, sessionmaker Base = declarative_base() # 一对多 class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=False) email = Column(String(32), unique=True) ctime = Column(DateTime, default=datetime.datetime.now) # 传递函数 extra = Column(Text, nullable=True) # 联级删除 groupId = Column(Integer, ForeignKey("usergroup.id", ondelete='CASCADE')) userGroup = relationship("UserGroup", backref="gusers") __table_args__ = { # 字符编码 'mysql_charset': 'utf8' # 引擎 # UniqueConstraint('id', 'name', name='uix_id_name'), # Index('ix_id_name', 'name', 'email'), } class UserGroup(Base): __tablename__ = 'usergroup' id = Column(Integer, primary_key=True) name = Column(String(50), nullable=False) # 多对多 class Grade(Base): __tablename__ = 'grade' id = Column(Integer, primary_key=True, autoincrement=True) score = Column(Integer, default=0) # 联级删除,一般不会直接删除关联表，而是将state设置为0 student_id = Column(Integer, ForeignKey('student.id', ondelete='CASCADE')) course_id = Column(Integer, ForeignKey('course.id', ondelete='CASCADE')) class Student(Base): __tablename__ = 'student' id = Column(Integer, primary_key=True) name = Column(String(64), nullable=False) # age = Column(Integer) # 与生成表结构无关，仅用于查询方便 courses = relationship('Course', secondary='grade', backref='students') class Course(Base): __tablename__ = 'course' id = Column(Integer, primary_key=True, autoincrement=True) course_name = Column(String(64), nullable=False) def init_db(): engine = create_engine( "mysql+cymysql://root:123@127.0.0.1:3306/sqlalchemy1?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收（重置） ) Base.metadata.create_all(engine) def del_db(): """ 根据类删除数据库表 :return: """ engine = create_engine( "mysql+cymysql://root:123@127.0.0.1:3306/sqlalchemy1?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收（重置） ) Base.metadata.drop_all(engine) def init_data1(): engine = create_engine("mysql+cymysql://root:123@127.0.0.1:3306/sqlalchemy1?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 方式一 # session.add_all([UserGroup(name='用户组1'), UserGroup(name='用户组2')]) # session.add_all([Users(name='admin', email='666@qq.com', extra='简介', groupId=1), # Users(name='admin', email='888@qq.com', extra='简介2', groupId=2),]) # 方式二 g1 = UserGroup(name='用户组3') g1.gusers = [Users(name='admin', email='777@qq.com', extra='简介', groupId=1)] session.add(g1) g2 = UserGroup(name='用户组4') g2.gusers = [Users(name='admin', email='999@qq.com', extra='简介2', groupId=2)] session.add(g2) session.commit() session.close() def init_data2(): engine = create_engine("mysql+cymysql://root:123@127.0.0.1:3306/sqlalchemy1?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 方式一 # session.add_all([Student(name='张三'), Student(name='李四'), ]) # session.add_all([Course(course_name='java'), Course(course_name='python'), ]) # # session.commit() # 这里必须先提交 # # session.add_all([Grade(student_id=1, course_id=1), # Grade(student_id=1, course_id=2), # Grade(student_id=2, course_id=1), ]) # 方式二 # 自动插入Grade数据，仅仅插入id stu1 = Student(name='张三') stu1.courses = [Course(course_name='java'), Course(course_name='python'), ] session.add(stu1) session.commit() session.close()
2.增删改查
# ################ 添加 ################ """ obj1 = Users(name="wupeiqi") session.add(obj1) session.add_all([ Users(name="wupeiqi"), Users(name="alex"), Hosts(name="c1.com"), ]) session.commit() """ # ################ 删除 ################ """ session.query(Users).filter(Users.id > 2).delete() session.commit() """ # ################ 修改 ################ """ session.query(Users).filter(Users.id > 0).update({"name" : "099"}) session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False) session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate") session.commit() """ # ################ 查询 ################
filter:表达式
filter_by:参数
动态参数：text(id<:value and name=:name)
执行原生SQL：session.query(Users).from_statement(text("select * from users where id=:value")).params(name='')
""" r1 = session.query(Users).all() r2 = session.query(Users.name.label('xx'), Users.age).all() r3 = session.query(Users).filter(Users.name == "alex").all() r4 = session.query(Users).filter_by(name='alex').all() r5 = session.query(Users).filter_by(name='alex').first() r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(Users.id).all() r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all() """
常用操作：
# 条件
in_
~ :非
ret = session.query(Users).filter_by(name='alex').all() ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all() ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all() ret = session.query(Users).filter(Users.id.in_([1,3,4])).all() ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()
# 连接查询 ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all() from sqlalchemy import and_, or_ ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all() ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all() ret = session.query(Users).filter( or_( Users.id < 2, and_(Users.name == 'eric', Users.id > 3), Users.extra != "" )).all() # 通配符 ret = session.query(Users).filter(Users.name.like('e%')).all() ret = session.query(Users).filter(~Users.name.like('e%')).all() # 限制 ret = session.query(Users)[1:2] # 排序 ret = session.query(Users).order_by(Users.name.desc()).all() ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all() # 分组 from sqlalchemy.sql import func ret = session.query(Users).group_by(Users.extra).all()
# 聚合函数 ret = session.query( func.max(Users.id), func.sum(Users.id), func.min(Users.id)).group_by(Users.name).all() ret = session.query( func.max(Users.id), func.sum(Users.id), func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all() # 连表 ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()
# 默认使用外键关系，连接查询 ret = session.query(Person).join(Favor).all()
# left join 左外连接 ret = session.query(Person).join(Favor, isouter=True).all()
ret = session.query(Person， Favor).join(Favor, Favor.id == Person.id, isouter=True).all()
ret = session.query(Person, Favor).join(Favor, and_(Person.id>1, Person.id==Favor.id).all() # 组合 q1 = session.query(Users.name).filter(Users.id > 2) q2 = session.query(Favor.caption).filter(Favor.nid < 2) ret = q1.union(q2).all() q1 = session.query(Users.name).filter(Users.id > 2) q2 = session.query(Favor.caption).filter(Favor.nid < 2) ret = q1.union_all(q2).all()
原生SQL：
import time import threading from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index from sqlalchemy.orm import sessionmaker, relationship from sqlalchemy import create_engine from sqlalchemy.sql import text from sqlalchemy.engine.result import ResultProxy from db import Users, Hosts engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 查询 # cursor = session.execute('select * from users') # result = cursor.fetchall() # 添加 cursor = session.execute('insert into users(name) values(:value)',params={"value":'wupeiqi'}) session.commit() print(cursor.lastrowid) session.close()
关联子查询：
获取课程最高分：
select id as cid, course_name, (select max(score) from grade where course_id=cid) as maxgrade from course
1.一对多
外键关系：
多对多关系：
book.py
user.py
关系表：gift.py
添加：db.session.add()
db.session.commit()
获取当前用户：current_user
事务回滚：
